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8/10/2019 Lect. 8 sun path
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Sun Path Diagram
8/10/2019 Lect. 8 sun path
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Sun Path
Sun pathrefers to the apparent significantseasonal-and-hourly positional changes of the
sun (and length of daylight) as the Earth rotates,
and orbits around the sun.
The relative position of the sun is a major factor in
the heat gainof buildings and in the performance
of solar energysystems.
http://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Solar_gainhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_gainhttp://en.wikipedia.org/wiki/Sun8/10/2019 Lect. 8 sun path
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Sun Path
Accurate location-specific knowledge of sun pathand climatic conditions is essential for
economic decisions about solar collectorarea,
orientation,
landscaping,
summer shading, and
the cost-effective use of solar trackers.
http://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/wiki/Solar_trackerhttp://en.wikipedia.org/wiki/Solar_trackerhttp://en.wikipedia.org/wiki/Solar_collector8/10/2019 Lect. 8 sun path
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Importance of Sun Path By analysing the impact of the sun on a site, as well
as the buildings location, the spatial arrangement,orientation, window placement, daylight access andother design features, the designer can take fulladvantage of passive solar design features and
increase the energy efficiency and comfort of thebuilding. assessing a site for sun
sun paths
altitude and azimuth solar radiation
building material durability
shade
sites with limited solar gain
locating information
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Assessing a site for sun
When assessing a site for sun, consider: the time during the day that the site receives
sunlight
the suns path at different times of the day and year
how the sites shape, slope and orientation affect
solar access
how obstructions such as adjacent buildings, trees
and landforms will impact on the site and the
potential design the owners lifestyle for example, when they want
to have sun or shade.
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Sun paths
The simplest way to assess the passage of sunacross a site is by observation.
A site visit can also help identify site-specific
conditions such as the impact of a tree or a
ridgeline.
Sun path diagrams provide a broader overview of
sun on a site as they map the path of the sun
across the sky at different times during the day
throughout the year.
They can help establish the position of the sun
relative to a site and can be used to determine
the effect of shadows cast by buildings, trees andlandforms on and around the site.
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Altitude and azimuth The position of the sun with respect to an observer is
commonly represented by two anglesaltitude and
azimuth.
Altitude is the angle of the suns rays compared with thehorizon. At sunrise and sunset, the altitude is zero, and
in the southern hemisphere, the maximum altitude of the
sun at any specific location occurs at solar noon on
21/22 December (longest days of the year).
Azimuth (sometimes known as bearing) is the direction
of the sun as shown on a compass. Sun bearings at
sunrise and sunset at different latitudes are available
from Land Information astronomical information.
http://www.linz.govt.nz/docs/hydro/nautical-info/astro/true-bearing-sr-ss.pdfhttp://www.linz.govt.nz/docs/hydro/nautical-info/astro/true-bearing-sr-ss.pdf8/10/2019 Lect. 8 sun path
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Solar radiation
Solar or ultraviolet (UV) radiation is the energyfrom the sun. The amount of solar radiation
available on a site depends on the latitude and
the sunlight hours received.
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Building material durability
UV radiation affects the durability of manymaterials. Colours fade, plastic-based materials
may become brittle, timber moves and twists, and
expansion and contraction from heating and
cooling places stress on many materials, so theeffect of UV radiation over a buildings lifetime
must be considered.
Select materials with a higher UV index number
(when available) as they are more resistant to UVdegradation (such as fading).
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Shade Shadeis often required in the summer, especially
in hot areas of our country. Obstructions on a sitemay block sunlight access at times when it isrequired.
When considering sunlight and building design,assess the impact of obstructions in the future aswell as the present. For example, a small tree onan adjacent site may grow into a large one thatblocks sun, a building may be erected on acurrently vacant site or an existing building maybe demolished and replaced by a larger one.
Alternatively, existing trees may be retained forsummer shade.
http://www.level.org.nz/passive-design/controlling-temperature/shade/http://www.level.org.nz/passive-design/controlling-temperature/shade/8/10/2019 Lect. 8 sun path
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Sites with limited solar access
South and west-facing, sloping sites have limitedsolar access.
It is difficult to utilise effective passive solar
design features on these sites, and they should
generally be avoided.
Where it is not possible to avoid or the site is an
otherwise desirable one (e.g. if it has excellent
views), careful consideration of design including
building location (e.g. locate as high as possible
on the site), orientation and use of
skylights/clerestories can maximise the benefits
of solar access.
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Locating information information about sunshine hours and mean
temperatures is available from local meteorologicalagencies/Dept. (IMD).
Aerial photographs can provide information about thebuildings and vegetation on adjacent sites and mayprovide some limited information about the impact ofsun on a site.
This will depend on the age of the photo as in olderphotos, trees may have grown.
Aerial images can be obtained from local councils,Google Earth, Etc..
Sun impact information is also available:
by carrying out an on-site survey to establish levels ofadjacent buildings and site features.
obtaining plans of neighbouring buildings from localcouncils.
http://www.localgovt.co.nz/http://earth.google.com/http://earth.google.com/http://www.localgovt.co.nz/8/10/2019 Lect. 8 sun path
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Sun Path Diagram for Mumbai